Park braking of a vehicle may be performed by means of a parking lock, integrated in the service brake actuator to form a unit therewith. Such a unit is known for use on trucks and buses. As is well known in the art, the parking brake may for example be a so-called spring brake actuator or an actuator with fluid actuation. The fluid normally used on heavy road vehicles is compressed air, but hydraulic fluid may equally well be utilized.
A special type of parking lock is the so-called lock actuator, with which the present invention is concerned. The function of a lock actuator is to lock the service brake actuator or parts thereof in an applied condition, in such a way that the service brake actuator will stay locked even in the absence of any fluid pressure. Thus, a parking brake is obtained.